Cold diesel engines are difficult to start. Leakage and heat losses due to the air being compressed reduce the final compression pressure and temperature to such a degree that the engine can no longer be started without the use of an auxiliary starting device. The lowest temperature threshold is a function of the engine design.
Various prior art devices have been employed to effect heat transfer to intake air of a diesel engine. One device employed to improve cold starting characteristics of diesel engines is a glow plug device. The glow plug is located within each combustion chamber of the diesel engine. Each of the glow plugs are connected in parallel to the vehicle battery. Power is applied to the glow plugs prior to engine cranking in order to raise the temperature of the plugs high enough to initiate fuel combustion.
A second known device employed to improve cold starting characteristics of diesel engines is a grid heater system. Heater grids are mounted in front of the air intake manifold of the engine to increase the inlet manifold air temperature. The grid heater system has the effect of heating the combustion air in the engine and improving starting performance when temperatures drop below the ambient temperature required for a diesel engine to ignite fuel.
Each of these heater systems are controlled differently. Automotive manufacturers, therefore, may be required to stock controllers for each of these heater systems when each of these heater systems are used for different vehicles. Thus, complexity is increased.